Bi-directional torque limiters

ABSTRACT

The combination, with a rotatable driving member and a cooperating rotatable driven member, of a bi-directional torque limiter which operates to limit the torque which can be transmitted from the driving to the driven member irrespective of the direction of rotation of the driving member, said torque limiter comprising a spring loaded connection between the driving and driven members which includes an element which normally partakes in the transmission of the drive but which, when the output torque reaches a predetermined limit, is arranged to move against spring action into engagement with a fixed element to relieve the driven member from the input torque.

Unite States Ptt Westbury 51 Apr. 4, 1972 [54] BI-DRECTIONAL TORQUELIMITERS [7 21 Inventor: Roy Westbury, Bridgnorth, England [73]Assignee: H. M. Hobson Limited, London, England [22] Filed: June 11,1970 [21] Appl. No.: 45,429

Primary Examiner-Edward G. Favors Attorney-Martin Kirpatrick [5 7]ABSTRACT The combination, with a rotatable driving member and acooperating rotatable driven member, of a bi-directional torque limiterwhich operates to limit the torque which can be transmitted from thedriving to the driven member irrespective of the direction of rotationof the driving member, said torque limiter comprising a spring loadedconnection between the driving and driven members which includes anelement which normally partakes in the transmission of the drive butwhich, when the output torque reaches a predetermined limit, is arrangedto move against spring action into engagement with a fixed element torelieve the driven member from the input torque.

2 Claims, 1 Drawing Figure Til-DIRECTIONAL TORQUE LIMITERS Thisinvention provides a bi-directional torque limiter which limits thetorque which may be transmitted by a rotatable driving member to arotatable driven member when the input torque available is greater thanthat acceptable to the mechanism driven by the driver member. The torquelimiter in accordance with the invention operates irrespective of thedirection of rotation of the driving member and it is alsobidirectional, i.e. it is effective when the inputs and outputs arereversed.

it comprises a spring loaded connection between the driving and drivenmembers which includes an element which normally partakes in thetransmission of the drive but which when the Output torque reaches apredetermined limit, is arranged to move against spring action intoengagement with a fixed element to relieve the driven member from theinput torque.

One embodiment of the invention is illustrated in the accompanyingdrawing, which is a longitudinal section through the torque limiter.

The apparatus illustrated comprises a stationary casing, consisting oftwo parts 10, 1 l which are fixed together by bolts 12 with anintervening stationary brake disc 13. An input shaft 14 is journalled ona bearing 15 and normally transmits rotation to a coaxial output shaft16 through the torque limiter. This consists of a spring pack 17,mounted in compression between a sleeve 18 on the output shaft 16 and arotary brake disc 19, and two sets of balls 20, 21 disposed on circlesof different diameter. The outer balls are accommodated in cups 22, 23disposed in opposed faces of the input shaft 14 and of the brake disc 19and the inner balls 21 are accommodated in cups 24, 25 disposed inopposed faces of the output shaft 16 and the brake disc 19. The shafts14, 16 are held against axial movement 50 long as the torque does notexceed a predetermined limit, the drive is transmitted from the inputshaft 14, via the outer set of balls 20, the disc 19 and the inner setof balls 21 to the output shaft 16 and the spring pack 17. When theoutput torque reaches a predetermined limit, the balls 20 will cooperatewith the inclined faces of the cups 23 to move the braking disc 19 tothe right against the action of the spring pack 17 until it engages thestationary braking disc 13. The members 19 and 13 are formed with teeth26, 27 which mesh to lock the mechanism and to stall the input torque,protecting the mechanism connected to the output shaft.

During normal operation the device thus acts as a straight through drivein both directions of rotation of the input shaft and also if the driveis applied to the shaft 16 instead of the shaft 14. It will operate asthe torque limiter in either direction of rotation, or from either end.The torque level at which locking occurs may be the same for bothdirections of rota tion. However a different torque level setting may beobtained in one direction of rotation as distinct from the otherdirection by appropriate shaping of the ball cups 23, 25.

The torque limiter illustrated is self resetting, since after the inputtorque has been stalled and the reacted torque has fallen to apredetermined level the spring pack 17 will cause it to revert to astraight through drive.

Alternatively the torque limiter could be so constructed as to maintainits locked condition until the input torque is deliberately reduced orreversed.

The torque limiter according to the invention is of general utility butis specifically intended for use in aircraft flap and slat controlsystems for the purpose of protecting the aircraft structure from thefull output torque of the actuating mechanism.

Iclaim:

l. The combination with a rotatable input shaft and a rotatable outputshaft coaxial with the input shaft, of a bidirectional torque limiterwhich operates to limit the torque which can be transmitted from theinput shaft to the output shaft irrespective of the direction ofrotation of the input shaft, said torque limiter comprising a stationerybraking member, a cooperating rotary braking disc spring urged away fromthe station braking member and two sets of balls arranged in circles 0different diameter, one set of balls being accommodated in cups in theface of the braking disc remote from the stationary braking member andin cups in an opposed face on the input shaft and the other set of ballsbeing accommodated in cups in said remote face of the braking disc andcups in an opposed face on the output shaft, said braking disc beingarranged to move against spring action into engagement which saidstationary braking member when the output torque attains a predeterminedlimit to relieve the output shaft from the input torque.

2. A combination as claimed in claim 1, in which said braking disc andsaid braking member are formed with teeth adapted to mesh uponengagement of the braking disc with the stationary braking member.

1. The combination with a rotatable input shaft and a rotatable outputshaft coaxial with the input shaft, of a bi-directional torque limiterwhich operates to limit the torque which can be transmitted from theinput shaft to the output shaft irrespective of the direction ofrotation of the input shaft, said torque limiter comprising a stationerybraking member, a cooperating rotary braking disc spring urged away fromthe stationary braking member and two sets of balls arranged in circlesof different diameter, one set of balls being accommodated in cups inthe face of the braking disc remote from the stationary braking memberand in cups in an opposed face on the input shaft and the other set ofballs being accommodated in cups in said remote face of the braking discand cups in an opposed face on the output shaft, said braking disc beingarranged to move against spring action into engagement which saidstationary braking member when the output torque attains a predeterminedlimit to relieve the output shaft from the input torque.
 2. Acombination as claimed in claim 1, in which said braking disc and saidbraking member are formed with teeth adapted to mesh upon engagement ofthe braking disc with the stationary braking member.